Handles foreign keys in POST of mappers

Author: aruhier

README.md

@@ -125,6 +125,26 @@ It is possible to get a subresourses of an object, and/or specify a query:
 
 Any `kwargs` (here `q=`) is used as a GET parameter for the request.
 
+#### Foreign keys
+
+Foreign keys are handle automatically by the mapper.
+
+```python
+>>> site = next(netbox_mapper.get())
+>>> print(site.region.name)
+"Some region"
+```
+
+When accessing to `site.region`, a query will be done to fetch the foreign
+object. It will then be saved in cache to avoid unnecessary queries for next
+accesses.
+
+To refresh an object and its foreign keys, just do:
+
+```python
+>>> site = next(site.get())
+```
+
 ### POST
 
 Use the `kwargs` of a mapper to send a post request and create a new object:
@@ -134,6 +154,9 @@ Use the `kwargs` of a mapper to send a post request and create a new object:
 <NetboxMapper>  # corresponding to the new created object
 ```
 
+If a mapper is sent as parameter, `post()` will automatically take its id.
+However, it will not update the foreign object.
+
 ### PUT
 
 Use `put()` in a child mapper to update the resource upstream by reflecting

netboxapi/mapper.py

@@ -84,6 +84,12 @@ def post(self, **json):
 
         :returns: child_mapper: Mapper containing the created object
         """
+        for k, v in json.items():
+            if isinstance(v, NetboxMapper):
+                try:
+                    json[k] = v.id
+                except KeyError:
+                    raise ValueError("Mapper {} has no id".format(k))
         new_mapper_dict = self.netbox_api.post(self._route, json=json)
         try:
             return next(self.get(new_mapper_dict["id"]))

tests/test_mapper.py

@@ -214,6 +214,34 @@ def update_or_create_resource_json_callback(self, request, context):
         json["id"] = 1
         return json
 
+    def test_post_foreign_key(self, mapper):
+        url = self.get_mapper_url(mapper)
+
+        fk_mapper = NetboxMapper(mapper.netbox_api, "foo", "bar")
+        fk_mapper.id = 2
+
+        with requests_mock.Mocker() as m:
+            received_req = m.register_uri(
+                "post", url, json={
+                    "id": 1, "name": "testname", "fk": {"id": 2}
+                }
+            )
+            m.register_uri(
+                "get", url + "1/",
+                json={
+                    "count": 1, "next": None, "previous": None,
+                    "results": [{
+                        "id": 1, "name": "testname", "fk": {
+                            "id": 2,
+                            "url": self.get_mapper_url(fk_mapper) + "2/"
+                        }
+                    }]
+                }
+            )
+            mapper.post(name="testname", fk=fk_mapper)
+
+        assert received_req.last_request.json()["fk"] == 2
+
     def test_put(self, mapper):
         child_mapper = self.get_child_mapper(mapper)
         url = self.get_mapper_url(child_mapper) + "{}/".format(child_mapper.id)